In a wide range of industry sectors, for example rubber manufacture, foodstuff production, etc., mixtures are produced in batch operation, for which various liquids are metered into a mixer. The mixer is intended to mix solids and liquids in a mixing process to form a homogeneous mass. In order to create reproducible masses, the manufacturer requires, besides the weighed solids, also an addition of one or more precisely metered liquids or fluids in order to impart specific properties to the end product that is then to be manufactured in a subsequent process.
Inter alia, weighing systems are known for the liquids to be metered. In said weighing systems, different fluids, in particular liquids, are metered and weighed one after the other into an intermediate container via separate feed lines, in order then to supply them as a whole to the mixer via a suitable conveying pump. At the time of a batch change, that is to say when another mixture is to be produced, the feed line is still filled with the old recipe. This means that a so-called intermediate mixture is obtained, which does not correspond to the previous mixture or to the new mixture.
Combined weighing and piston systems are also known on the market, in which firstly a container on a set of scales is filled with the appropriate quantity of a liquid for a specific mixture, then this liquid from the weighing container is buffer-stored in a so-called metering cylinder by means of a conveying pump and is checked once again with regard to the desired quantity in order then to be fed to the mixer after the shot has been approved. This method is therefore a combined metering system which operates gravimetrically and volumetrically.
Also known are piston metering systems which are controlled by means of a mass through-flow measuring system. However, these measuring systems, which operate according to the Coriolis principle, are often not accurate enough in challenging industrial operations, in particular due to shaking or vibrations, or falsify the result during shot operation since the systems often have to be smoothed or filtered electronically or by means of software.
The systems described above are based predominantly on gravimetric metering or measurement, with the advantages and disadvantages known in industry.